The present invention relates to a decorative film that is used as a surface layer of an interior part of a vehicle to decorate the interior part.
Some vehicle interior parts have decorative films as surface layers. FIG. 5 shows an example of a decorative film that includes an opaque substrate 51 and a transparent decorative layer 57. The opaque substrate 51 includes an uneven section 52 on the surface. The transparent decorative layer 57 is stacked on the surface (the upper side as viewed in FIG. 5) of the opaque substrate 51 and closely contacts the uneven section 52.
The uneven section 52 typically includes projections 53, each having a square flat top surface 54, and depressions 55, each having a square flat bottom surface 56. The projections 53 and the depressions 55 are arranged alternately. With the decorative film 50, a portion of the light that is incident on the transparent decorative layer 57 from the surface side of the decorative film 50 is reflected from the top surfaces 54 of the projections 53, and another portion of the light is reflected from the bottom surfaces 56 of the depressions 55, which are at a greater depth than the top surfaces 54. Thus, the top surfaces 54 and the bottom surfaces 56 are perceived as three-dimensional patterns of two types of squares that are arranged alternately below the surface of the decorative film 50. This improves the texture of the interior part.
Examples of the related art include Japanese Laid-Open Patent Publication No. 2013-132820, which describes a decorative sheet that includes a transparent print layer and a colored print layer.
The three-dimensional appearance of patterns described above is achieved effectively when the opaque substrate 51 has a light color. This is because the large difference in the light reflection characteristics, such as reflection directions, between the top surfaces 54 and the bottom surfaces 56 clarifies the difference in shading.
On the other hand, the patterns of the top surfaces 54 and the bottom surfaces 56 are perceived to be located at a greater depth from the surface of the decorative film 50 when the opaque substrate 51 has a dark color instead of a light color. However, when a dark color is used for the opaque substrate 51, which forms simple patterns in which square flat top surfaces 54 and square flat bottom surfaces 56 are arranged alternately, the difference in shading between the pattern of the top surfaces 54 and the pattern of the bottom surfaces 56 is not clear. This disadvantageously results in the patterns perceived as having the same dark color.